DE19528437A1 - Method for operating a data transmission system - Google Patents

Abstract

The invention concerns a process for operating a data transmission system with a plurality of stations (1, 2, 3, 4) connected to one another via a common bus line, only one subscriber (1) at any given time having right of access to the bus line and controlling data transmission over the bus line with polling messages (5) sent to several other stations (2, 3, 4) simultaneously. The response times (7, 8, 9) of the called stations (2, 3, 4) are determined. The called stations (2, 3, 4) are so parameterized that they acknowledge or answer the polling message (5) in order of their response times with reply messages (13, 14, 15). The invention is applicable to field buses in automation technology.

Description

The invention relates to a method for operating a Da Transmission system according to the preamble of claim 1.

Such a method for operating a data transmission system is already known from DE-OS 42 13 792. A data telegram (COP) called there by a subscriber who is in possession of the bus access right transfers several data for different other subscribers. The other participants, who have been requested by the sum frame telegram to transmit a response telegram, send their response telegrams one after the other in a predetermined sequence in time slots of fixed duration on the bus line. Hardware coding by the user during commissioning, parameterization in the initialization phase or a definition depending on the subscriber addresses are mentioned as options for determining this sequence. As a feasible variant with little effort, the direct mapping of the subscriber addresses to the time slot numbers is highlighted, so that the time slot, beginning at time t1, the subscriber with address 1 , the time slot at t2 is assigned to those with address 2 etc. . The known method is already an improvement in the transmission speed, but it is not yet an optimal solution.

The invention has for its object a method for Operating a data transmission system to find the the transmission speed is further increased.

To solve this problem with the new method type mentioned in the characterizing part of the An claim 1 specified feature provided. In the subclaims  Chen are advantageous developments of the invention wrote.

The invention has the advantage that the order of the ant worded participant is time-optimized. It can at for example, it does not happen that a participant with very short response time due to a high subscriber address Transmission of his data must wait until slow participation have reacted and transferred their data. Since often the actual transmission times compared to the internal loading working time of a call telegram by the called Participants are low, the invention for a Processing a call telegram to several other participants more time required from the slowest response time Participant determined. It can in the calling participant the occurrence of none, one or more answering telephones grams that arrive one after the other or overlap in time mastered. A method is specified with a participant in bus systems data of one or more Collect more participants, one participant data distribute to one or more participants at the same time Participant data to one or more participants at the same time distribute and collect data from these participants Participants determine the presence of other participants and a participant certain characteristics of other participants can query. In addition, other applications of the Process conceivable and possible. The expression "multiple part "means a group of at least two and maxi times all other connected participants.

Based on the drawings, in which embodiments of the Er are shown, the invention are the following as well as configurations and advantages explained in more detail.

Fig. 1 shows the timing of a transmission with successively arriving response messages,

Fig. 2 shows a sequence with overlapping response telegrams.

In the two drawings, the positions of participants are 1 . . . 4 represented by vertical lines and the transfer directions and times of telegrams by arrows next to a vertical time axis t.

In Fig. 1 a subscriber 1 invoking addressed ruftelegramm 5, arrives at more other subscriber 2, 3 and 4 is about the same for these on a. Only those participants who meet a certain selection criterion, which will be explained in more detail later, are addressed. The following responses to call telegram 5 , which can be determined for the calling subscriber 1, are possible in principle:

• - No response telegram within a specified waiting time 6 ,
• - Reply telegram from a participant within the specified waiting time 6 and
• - Reply telegrams from several, possibly all called participants 2 , 3 or 4 within the specified waiting time 6 .

Which of these cases represent good or bad cases and how any responses that may have been interpreted and evaluated depends on the respective application. If there is the possibility of at least one answer, the waiting time 6 begins at the calling subscriber 1 , which is dimensioned such that the called subscriber 2 . . . 4 can respond within this waiting time 6 if the operation is faultless If one or more answers arrive after this waiting time 6 has elapsed, then this is interpreted as faulty behavior of the participants 2 , 3 or 4 concerned .

The procedure can be carried out in the data access protocol (layer 2 of the 7-layer model) of the individual participants or in the application (in layers 3 ... 7). The reaction to the arrival of call or response telegrams must be determined in each individual case according to the respective needs. In the calling subscriber, the reaction only takes place after the waiting time 6 described has elapsed, even if the reason for this already exists earlier. If e.g. B. the process is entirely in the data access log, a request from the user can trigger the process, and after the waiting time 6 , a reaction to the user can take place as confirmation. The impetus does not necessarily have to come from the user either.

Call telegram 5 contains at least the following parts:

• - Source address (bus address of the calling subscriber) and
• - Destination address (e.g. global address for addressing everyone at closed participants).

The following additional components can optionally be available be:

• - selection criterion,
• - Implementing regulation and
• - Data.

The selection criterion is used to select the addressed participants. It determines whether a single participant, a group of participants or all participants is addressed and, if necessary, which participants make up a group. A selection criterion can e.g. B. be an identifier for a specific access channel in the subscriber, similar to an LSAP (Link Service Access Point) of the PROFIBUS, which is used there for multicast telegrams. Then all participants are addressed for whom the required function is activated on this access channel. The selection criterion is optional in call telegram 5 . If it is not broadcast, participants 2 , 3 and 4 must be known in another way, e.g. B. by implicit determination.

The execution regulation serves to communicate the desired response to the called participants. examples for Implementation regulations are:

• - collect data from multiple participants,
• - transmit data to several other participants,
• - collect and transmit data from several participants,
• - Create participant image and
• - test.

This list can be determined by further implementing regulations be expanded. Also combinations of already defined ones Regulations are possible.

The execution instruction does not have to be sent in the call telegram 5 . You can be known to the called participants 2 , 3 and 4 in other ways, for. B. by implicit limitation to only one specific rule or if the rule depends on the selection criterion or the state of the participants.

The transmitted data can be pure user data or also contain components that are required to implement the be written procedure. They are optional, e.g. B. become none at the first mentioned regulation Transfer data in the request telegram.

The method is carried out according to the "immediate response" principle, ie no other traffic takes place on the bus between the call telegram and the response telegram or the expiration of the waiting time 6 . The required waiting time 6 can therefore be calculated if the reaction times of the called subscribers 2 , 3 and 4 and the transmission times of the response telegrams are known. Repetitions of the telegram transmissions are e.g. B. due to transmission errors, possible.

The reaction times of the called subscribers 2 , 3 and 4 are indicated in Fig. 1 by vertical, dotted lines 7, 8 and 9 respectively. The answers of various called up participants appear one after the other on the bus. This is achieved in that for each called subscriber 2 , 3 or 4, a time window 10 , 11 or 12 is specified in which he can answer. Gaps between time slots 10 , 11 and 12 are permitted, but should not overlap. Each called participant 2 , 3 and 4 must know his own time window 10 , 11 and 12 , but not the time window of other called participants. Outside the allocated time window, none of the called up participants may answer. The calling subscriber 1 does not have to know the individual time windows 10 , 11 or 12 , but the waiting time 6 for answers 13 , 14 and 15 , which must be large enough to enable all called subscribers to respond within this time. In the calling subscriber 1 , a list with the called subscribers 2 , 3 and 4 can also be kept, e.g. B. to check whether all called participants have responded.

The time windows 10 , 11 and 12 must be configured and coordinated with each other for the individual case. The response times 7 , 8 and 9 and the transmission times of the response telegrams 13 , 14 and 15 must be taken into account. In general, they should be selected so that the response telegrams cannot overlap. The order of the time windows 10 , 11 and 12 is determined by the response times 7 , 8 and 9 of the called subscribers 2 , 3 and 4 , to whom they are assigned. The first time window, here time window 10 , is assigned to the called subscriber who has the shortest reaction time, in this case subscriber 2 . There are several options for determining the individual response times. You can e.g. B. in each participant 1 . . . 4 be permanently stored and are read out in an initialization phase by the calling subscriber 1 or a configurator. It is also possible to determine the response times of individual participants by calling telegrams. With this information and the bus transmission time, the location of the respective time window can easily be determined and transmitted to the called subscribers 2 , 3 and 4 .

If with a request telegram only data is to be distributed to several participants at the same time, the relevant data are contained in the request telegram 5 , the receipt of which is acknowledged with response telegrams 13 , 14 and 15 , which do not contain any data, of the requested participants 2 , 3 or 4 becomes.

To collect data, the calling subscriber 1 sends a request to the other subscribers 2 , 3 and 4 to return data and receives the desired data in the response telegrams 13 , 14 and 15 respectively. The response telegrams must arrive one after the other in the respective time windows 10 , 11 or 12 so that they do not interfere with each other. A sequential query of individual participants is not necessary. A call telegram 1 is sufficient to query several participants.

If the calling subscriber 1 is to both distribute and collect data, the call data 5 and the response telegrams 13 , 14 and 15 contain the respective data.

To test for certain subscriber properties or features, subscriber 1 according to FIG. 2 sends a search request telegram 16 to all other subscribers 2 , 3 and 4 , which may contain an indication of the subscriber feature searched for as data. This allows participants to access features such. B. bus address, serial number, presence of a certain functionality, manufacturer, are checked. All subscribers that have this feature respond to the search request telegram 16 . The answers can come one after the other or overlap, depending on the type of search. If the calling participant 1 z. B. wants to know whether no, one or more participants have a required property, for. B. to test for multiple existence of the same bus address, the answers can be overlapping. This is illustrated in Fig. 2 for response telegrams 17 and 18 with an overlap area 19 ver.

If the calling subscriber 1 z. B. wants to know how many participants are present on the bus with a certain property, for example, to test for a particular manufacturer, the called participants 2 , 3 and 4 in the assigned time windows 10 , 11 and 12 according to FIG. 1, their response telegrams 13 , 14 or 15 so that the number of responses can be clearly determined.

To create a current subscriber image, the calling subscriber 1 according to FIG. 1 sends a call telegram 5 to all other subscribers in order to determine their existence or functionality. All existing and functional participants, in this case participants 2 , 3 and 4 , respond with an acknowledgment as response telegram 13 , 14 or 15 to indicate this. The acknowledgments must arrive one after the other so that they do not interfere with each other and the calling subscriber 1 can distinguish between the individual response telegrams 13 , 14 and 15 . Time slots 10 , 11 and 12 are therefore used. Since no individual calls are required for each individual subscriber in the method according to the invention for the creation of a subscriber image, the entire subscriber image is created at virtually the same time. The subscriber image is consistent, since the response telegrams arrive in a very short period of time and the status of the subscriber can hardly change during this time, for example due to a new connection or failure of a subscriber.

In the example according to FIG. 2, it is to be checked whether several participants have bus address 22 . The call telegram 16 contains this bus address as a feature in the data field. The two participants 3 and 4 have the address 22 and therefore respond to the search request. All other participants do not answer. In this case, overlaps are allowed, since it is only of interest whether more than one participant answers. If overlaps are permissible, there must be a uniqueness criterion that is sent in the response telegrams and guarantees that the response telegrams of different called participants differ. It must therefore have the property that it is different for all participants involved. Examples of such uniqueness criteria are:

• - Serial number,
• - Unique identifier assigned in the system of the called Attendees,
• - a special criterion determined by the user and
• - A quasi-unique randomness generated in the participants number with a large display range.

Combinations of the examples mentioned are also possible. Since with it can be seen even with complete overlap of two or more messages that there are several responses th, because there is at least one place in the information received by the calling subscriber 1 , which is an overlap, for example, as a bus fault or unidentifiable Makes telegram noticeable.

Claims (7)

1. Method for operating a data transmission system, in particular for a programmable logic controller,

• - With a large number of participants connected to one another via a common bus line ( 1 ... 4 ), of whom only one ( 1 ) is in possession of the right of access to the bus line at a certain time and data transmission via the bus line Control telegrams ( 5 ), which are directed to several other participants ( 2 , 3 , 4 ) simultaneously, controls

characterized,

• - That the response time ( 7 , 8 , 9 ) of each called subscriber ( 2 , 3 , 4 ) is determined and the called subscriber mer ( 2 , 3 , 4 ) are parameterized such that they call the telegram ( 5 ) in the Acknowledge or answer the sequence of their response times in succession, so that the subscriber ( 2 ) with the shortest response time ( 7 ) is the first and the subscriber ( 4 ) with the longest response time ( 9 ) is the last to access the bus.

2. The method according to claim 1, characterized in that

• - That in an initialization phase each participant ( 2 , 3 , 4 ) is called individually to determine its response time ( 7 , 8 , 9 ) by means of a call telegram.

3. The method according to claim 1 or 2, characterized in that

• - That each called subscriber ( 2 , 3 , 4 ) is given a time window ( 10 , 11 , 12 ) through which it is determined when he may access the bus after the end of the call telegram ( 5 ).

4. The method according to claim 3, characterized in that

• - That after the elapse of the last time window ( 12 ), that is, after a predetermined waiting time ( 6 ) of calling the subscriber ( 1 ), it is checked whether all called subscribers ( 2 , 3 , 4 ) acknowledge or answer the call telegram ( 5 ) and - if not - an error handling routine is initiated.

5. The method according to any one of the preceding claims, characterized in that

• - that a subscriber (1) to all other participants (2, 3, 4) a search call message (5, 16) sends that contains a feature statement in its data, and all other users (2, 3, 4), the feature ( e.g. bus address, serial number, availability of a certain functionality, manufacturer) matches the specification of the characteristics, answer the search request simultaneously or in succession.

6. The method according to any one of the preceding claims, characterized in that

• - That a subscriber ( 1 ) to all other subscribers ( 2 , 3 , 4 ) sends a call telegram ( 5 ) to create a subscriber image and all other subscribers ( 2 , 3 , 4 ) acknowledge this call telegram one after the other and there by their Show existence and functionality.